The parts used for the project are:
1 - 16 pin DIP parts header
1 - 24 pin DIP socket
1 - piece of standard .1 inch perforated board (cut to size)
2 - plastic printed circuit board standoffs
2 - small miscellaneous screws
miscellaneous 26 and 22 gage wires
epoxy
1 - 2716 or 27C16 EPROM
Soldering is required for this project. The common plastic 16 pin DIP headers tend to melt if the solder iron tip is held on a pin too long, so quick efficient soldering is required. Since I am right handed (my soldering iron hand) I found it easiest to start with the 16 pin DIP header pins on my left and work across one pin at a time (i.e. pins 9-16 and pins 1-8). Because pins 10 through 12 and pin 15 have to cross to the other side on the 24 pin DIP socket I found it easier to start wiring with 16 pin DIP header pins 9 through 16.
Depending on the parts you have or can find you may have to improvise. I found all these parts just by cruising up and down the isles at a local electronics supply company.
First the perforated board was cut to size (see photos). Then the printed circuit board standoffs were cut down (they were originally too long) and screwed to the perforated board. Next the standoffs were glued to the 16 pin DIP parts header. Then the 24 pin DIP socket was placed on the perforated board and the pins were wired from point to point. The 22 gage wire was used for the Vcc and Gnd1 pins. The 26 gage wire was used for all the other pins. Be sure to check for clearance with components on the Syntor circuit board when cutting the standoffs to size.
Here is the wiring diagram:
Just connect all of the identicaly named pins (ignore the information
in light gray) from the 16 pin header to the 24 pin socket.
The Vcc and Vpp on the 24 pin socket are also connected together.
nc - not connected (the original PROM is only 4 bits wide)
Here are the EPROM converter photos:
Photos by: Max KK7HI
Please take note that pin 1 on the 16 pin DIP header is shaved (this one came that way) and the 24 pin DIP socket above it oriented with its pin 1 orientation notch above the 16 pin header pin 1 end. When the 24 pin EPROM is installed, its pin 1 orientation notch matches the pin 1 orientation notch in the 24 pin socket and the 16 pin header is plugged in with its pin 1 where the old PROM pin 1 would have gone. This is done on purpose to avoid confusion about orienting pin 1 correctly on the EPROM and when plugging it into the Syntor socket. The Syntor 16 pin socket can be hard to see when plugging in the conversion assembly so using a flashlight is recommended to help visually verify the 16 pin header is correctly installed in the Syntor 16 pin socket.
The EPROM converters are a bit labor intensive to build, but they will forever free you from trying to find and program those old PROMs. Needless to say the larger EPROM will provide up to 32 channels and they are so common almost all programmers will program them. After the conversion you can erase the EPROM with an ultraviolet eraser and reprogram it rather then the old method of having to throw out the old disposable PROMs and then find and program brand new PROMs.
It does not look pretty, but it does not have to look pretty to get the job done.
To enable 32 channel operation JU1101 (near the old PROM) will have to be removed. When it is installed it grounds address line A8 and only allows 16 channel operation. A 32 channel control head and cable with 12 frequency select lines is required for proper operation when JU1101 is removed.
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